System and method for voice over internet protocol (VoIP) and facsimile over internet protocol (FoIP) calling over the internet

ABSTRACT

A system and method for sending long distance telephone calls over the Internet utilizes cost and quality of service data to optimize system performance and to minimize the cost of completing the calls. The system utilizes a network of gateways connected to the Internet. The gateways receive calls from various service providers and convert the analog calls into data packets which are then placed onto the Internet. Similarly, the gateways take data packets off the Internet, convert the data packets back into analog format, and provide the analog telephone calls to the same or another service provider. The system periodically checks the quality of communications between each of the gateways, and uses this information, in combination with cost information, to determine how to route the calls over the Internet. Special addressing protocols can be used by a system embodying the invention to reduce or eliminate unnecessary signaling between gateways as call setup procedures are carried out.

This application is a continuation-in-part of U.S. application Ser. No.10/298,208, filed Nov. 18, 2002, the disclosure of which is herebyincorporated by reference. The application also claims priority to U.S.Provisional Patent Application Ser. No. 60/331,479, filed Nov. 16, 2001,and U.S. Utility application Ser. No. 10/094,671, filed Mar. 7, 2002,the disclosure of both of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to the field of communications, and morespecifically to a network configured for Voice over Internet Protocol(VoIP) and/or Facsimile over Internet Protocol (FoIP).

2. Background of the Related Art

Historically, most wired voice communications were carried over thePublic Switched Telephone Network (PSTN), which relies on switches toestablish a dedicated circuit between a source and a destination tocarry an analog or digital voice signal. In the case of a digital voicesignal, the digital data is essentially a constant stream of digitaldata. More recently, Voice over Internet Protocol (VoIP) was developedas a means for enabling speech communication using digital,packet-based, Internet Protocol (IP) networks such as the Internet. Aprinciple advantage of IP is its efficient bandwidth utilization. VoIPmay also be advantageous where it is beneficial to carry related voiceand data communications over the same channel, to bypass tollsassociated with the PSTN, to interface communications originating withPlain Old Telephone Service (POTS) with applications on the Internet, orfor other reasons. As discussed in this specification, the problems andsolutions related to VoIP may also apply to Facsimile over InternetProtocol (FoIP).

Throughout the description that follows there are references to analogcalls over the PSTN. This phrase could refer to analog or digital datastreams that carry telephone calls through the PSTN. This isdistinguished from VoIP or FoIP format calls, which are formatted asdigital data packets.

FIG. 1 is a schematic diagram of a representative architecture in therelated art for VoIP communications between originating telephone 100and destination telephone 145. In alternative embodiments, there may bemultiple instances of each feature or component shown in FIG. 1. Forexample, there may be multiple gateways 125 controlled by a singlecontroller 120. There may also be multiple controllers 120 and multiplePSTN's 115. Hardware and software components for the features shown inFIG. 1 are well-known. For example, controllers 120 and 160 may be CiscoSC2200 nodes, and gateways 125 and 135 may be Cisco AS5300 voicegateways.

To initiate a VoIP session, a user lifts a handset from the hook oforiginating telephone 100. A dial tone is returned to the originatingtelephone 100 via Private Branch Exchange (PBX) 110. The user dials atelephone number, which causes the PSTN 115 to switch the call to theoriginating gateway 125, and additionally communicates a destination forthe call to the originating gateway 125. The gateway will determinewhich destination gateway a call should be sent to using a look-up tableresident within the gateway 125, or it may consult the controller 120for this information.

The gateway then attempts to establish a call with the destinationtelephone 145 via the VoIP network 130, the destination gateway 135,signaling lines 155 and the PSTN 140. If the destination gateway andPSTN are capable of completing the call, the destination telephone 145will ring. When a user at the destination telephone 145 lifts a handsetand says “hello?” a first analog voice signal is transferred through thePSTN 140 to the destination gateway 135 via lines 155. The destinationgateway 135 converts the first analog voice signal originating at thedestination telephone 145 into packetized digital data (not shown) andappends a destination header to each data packet. The digital datapackets may take different routes through the VoIP network 130 beforearriving at the originating gateway 125. The originating gateway 125assembles the packets in the correct order, converts the digital data toa second analog voice signal (which should be a “hello?” substantiallysimilar to the first analog signal), and forwards the second analogvoice signal to the originating telephone 100 via lines 155, PSTN 115and PBX 110. A user at the originating telephone 100 can speak to a userat the destination telephone 145 in a similar manner. The call isterminated when the handset of either the originating telephone 100 ordestination telephone 145 is placed on the hook of the respectivetelephone. In the operational example described above, the telephone 105is not used.

In the related art, the controllers 120 and 160 may provide signalingcontrol in the PSTN and a limited means of controlling a gateway at oneend of the call. It will be appreciated by those skilled in the artthat, in some configurations, all or part of the function of thecontrollers 120 and 160 as described above may be embedded into thegateways 125 and 135, respectively.

VoIP in the related art presents several problems for a provider ofnetwork-based voice communication services. For example, because packetsof information follow different routes between source and destinationterminals in an IP network, it is difficult for network serviceproviders to track data and bill for network use. In addition, VoIPnetworks in the related art lack adequate control schemes for routingpackets through the Internet based upon the selected carrier serviceprovider, a desired Quality of Service (QoS), cost, and other factors.Moreover, related art controllers do not provide sufficient interfacesbetween the large variety of signaling systems used in internationalcommunications. Other disadvantages related to monitoring and controlalso exist with present VoIP schemes.

SUMMARY OF THE INVENTION

An object of the invention is to solve at least one or more of the aboveproblems and/or disadvantages in whole or in part and to provide atleast the advantages described hereinafter.

Another object of the invention is to provide an improved ability toidentify the best routes for VoIP and FoIP traffic through a networkbased on a variety of considerations.

Another object of the invention is to provide an improved ability toprovision a network in order to direct VoIP and FoIP traffic accordingto the identified best routes.

Another object of the invention is to provide improvedacceptance/decline logic for determining whether to route traffic uponreceipt of a routing request.

In order to achieve at least the above objectives in whole or in partand in accordance with the purposes of the invention, as embodied andbroadly described, an improved control architecture for VoIP/FoIPcommunications is provided including the features of: a control signalinterface to at least one gateway for routing VoIP/FoIP communicationsover an IP network. A gatekeeper may be coupled to the control signalinterface, and control means coupled to the gatekeeper, wherein thecontrol means is configured to receive a VoIP/FoIP routing request,determine a best route through the IP network, provision the IP networkfor the determined best route, and analyze traffic on the IP network.

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objects and advantages of the invention may be realizedand attained as particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in detail with reference to thefollowing drawings in which like reference numerals refer to likeelements, and wherein:

FIG. 1 is a schematic diagram of a system architecture providing VoIPcommunications, according to the background;

FIG. 2 is a schematic diagram of a system architecture providingVoIP/FoIP communications, according to a preferred embodiment of theinvention;

FIG. 3 is a schematic diagram of a system architecture providingimproved control for VoIP communications, according to a preferredembodiment of the invention;

FIG. 4 is a flow diagram illustrating a method for routing control,according to a preferred embodiment of the invention;

FIG. 5 is a flow diagram illustrating a method for maintaining a callstate, according to a preferred embodiment of the invention;

FIG. 6 is a sequence diagram illustrating a method for communicatingbetween functional nodes of a VoIP network, according to a preferredembodiment of the invention;

FIG. 7 is a flow diagram illustrating a three level routing method,according to a preferred embodiment of the invention;

FIG. 8 is a schematic diagram of a system architecture embodying theinvention;

FIG. 9 is a diagram of a matrix illustrating a method for organizingquality of service data for communications paths between gateways;

FIGS. 10A and 10B are flow diagrams of alternate methods of obtainingquality of service data for alternate communications paths;

FIG. 11 is a flow diagram of a method for making routing decisionsaccording to a preferred embodiment of the present invention; and

FIG. 12 is a schematic diagram of a system architecture for routingtraffic over the Internet, according to a second embodiment of thepresent invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

A system embodying the invention is depicted in FIG. 2. The systemincludes telephones 100/105 connected to a private branch exchange (PBX)110. The PBX, in turn, is connected to the PSTN 115. In addition,telephones 102 may be coupled to a local carrier 114, which in turnroutes long distance calls to one or more long distance serviceproviders 117. Those skilled in the art will recognize that calls couldalso originate from cellular telephones, computer based telephones,and/or other sources, and that those calls could also be routed throughvarious carriers and service providers. Regardless of where the callsare originating from, they are ultimately forwarded to an originatinggateway 125/126.

The originating gateways 125/126 function to convert an analog call intodigital packets, which are then sent via the Internet 130 to adestination gateway 135/136. In some instances, the gateways may receivea call that has already been converted into a digital data packetformat. In this case, the gateways will function to communicate thereceived data packets to the proper destination gateways. However, thegateways may modify the received data packets to include certain routingand other formatting information before sending the packets on to thedestination gateways.

The gateways 125/126/135/136 are coupled to one or more gatekeepers205/206. The gatekeepers 205/206 are coupled to a routing controller200. Routing information used to inform the gateways about where packetsshould be sent originates at the routing controller.

One of skill in the art will appreciate that although a single routingcontroller 200 is depicted in FIG. 2, a system embodying the inventioncould include multiple routing controllers 200. In addition, one routingcontroller may be actively used by gatekeepers and gateways to providerouting information, while another redundant routing controller may bekept active, but unused, so that the redundant routing controller canstep in should the primary routing controller experience a failure. Aswill also be appreciated by those skilled in the art, it may beadvantageous for the primary and redundant routing controllers to belocated at different physical locations so that local conditionsaffecting the primary controller are not likely to also result infailure of the redundant routing controller.

In a preferred embodiment of the invention, as depicted in FIG. 2, thedigital computer network 130 used to communicate digital data packetsbetween gateways may be compliant with the H.323 recommendation from theInternational Telecommunications Union (ITU). Use of H.323 may beadvantageous for reasons of interoperability between sending andreceiving points, because compliance with H.323 is not necessarily tiedto any particular network, platform, or application, because H.323allows for management of bandwidth, and for other reasons. Thus, in apreferred embodiment, one function of the originating gateways 125 and126 and the terminating gateways 135 and 136 may be to provide atranslation of data between the PSTN's 115/135 and the H.323-based VoIPnetwork 130. Moreover, because H.323 is a framework document, the ITUH.225 protocol may be used for communication and signaling between thegateways 125/126 and 135/136, and the IETF RTP protocol may be used foraudio data between the gateways 125/126 and 135/136, and RAS(Registration, Admission, and Status) protocol may be used incommunications with the gatekeepers 205/206.

According to the invention, the gatekeeper 205 may perform admissioncontrol, address translation, call signaling, call management, or otherfunctions to enable the communication of voice and facsimile trafficover the PSTN networks 115/140 and the VoIP network 130. The ability toprovide signaling for networks using Signaling System No. 7 (SS7) andother signaling types may be advantageous over network schemes that relyon gateways with significantly less capability. For example, related artgateways not linked to the gatekeepers of the present invention may onlyprovide signaling for Multi-Frequency (MF), Integrated Services DigitalNetwork (ISDN), or Dual Tone Multi-Frequency (DTMF).

According to a preferred embodiment of the present invention, thegatekeeper 205 may further provide an interface between differentgateways, and the routing controller 200. The gatekeeper 205 maytransmit routing requests to the routing controller 200, receive anoptimized route from the routing controller 200, and execute the routeaccordingly.

Persons skilled in the art of communications will recognize thatgatekeepers may also communicate with other gatekeepers to manage callsoutside of the originating gatekeeper's area of control. Additionally,it may be advantageous to have multiple gatekeepers linking a particulargateway with a particular routing controller so that the gatekeepers maybe used as alternates, allowing calls to continue to be placed to allavailable gateways in the event of failure of a single gatekeeper.Moreover, although the gatekeeping function may be logically separatedfrom the gateway function, embodiments where the gatekeeping and gatewayfunctions are combined onto a common physical host are also within thescope of the invention.

In a system embodying the present invention, as shown in FIG. 2, arouting controller 200 is logically coupled to gateways 125/126 and135/136 through gatekeepers 205/206. The routing controller 200 containsfeatures not included in the prior art signaling controllers 120 and 160of the prior art systems described above, as will be described below.Routing controller 200 and gatekeepers 205/206 may be hosted on one ormore network-based servers which may be or include, for instance, aworkstation running the Microsoft Windows™ NT™, Windows™ 2000, Unix,Linux, Xenix, IBM AIX™, Hewlett-Packard UX™, Novell Netware™, SunMicrosystems Solaris™, OS/2™, BeOS, Mach, Apache, OpenStep™, JavaVirtual Machine or other operating system or platform. Detaileddescriptions of the functional portions of a typical routing controllerembodying the invention is provided below.

As indicated in FIG. 3, a routing controller 200 may include a routingengine 305, a Call Detail Record (CDR) engine 325, a traffic database330, a traffic analysis engine 335, a provisioning engine 340, and aprovisioning database 345. The routing engine 305, CDR engine 325,traffic analysis engine 335, and provisioning engine 340 may exist asindependent processes and may communicate to each other through standardinterprocess communication mechanisms. They might also exist onindependent hosts and communicate via standard network communicationsmechanisms.

In alternative embodiments, the routing engine 305, Call Detail Record(CDR) engine 325, traffic database 330, traffic analysis engine 335,provisioning engine 340, or provisioning database 345 may be duplicatedto provide redundancy. For instance, two CDR engines 325 may function ina master-slave relationship to manage the generation of billing data.

The routing engine 305 may include a communications layer 310 tofacilitate an interface between the routing engine 305 and thegatekeepers 205/206. Upon receipt of a routing request from agatekeeper, the routing engine 305 may determine the best routes forVoIP traffic based upon one or more predetermined attributes such as theselected carrier service provider, time of day, a desired Quality ofService (QoS), cost, or other factors. The routing information generatedby the routing engine 305 could include a destination gateway address,and/or a preferred Internet Service Provider to use to place the calltraffic into the Internet. Moreover, in determining the best route, therule engine 315 may apply one or more exclusionary rules to candidateroutes, based upon known bad routes, provisioning data from provisioningdatabase 345, or other data.

The routing engine 305 may receive more than one request to route asingle call. For example, when a first routing attempt was declined bythe terminating gateway, or otherwise failed to result in a connection,or where a previous routing attempt resulted in a disconnect other thana hang-up by the originator or recipient, then the routing engine mayreceive a second request to route the same call. To provide redundancy,the routing engine 305 may generate alternative routes to a particularfar-end destination. In a preferred embodiment of the invention, whenthe routing engine receives a routing request, the routing engine willreturn both preferred routing information, and alternative routinginformation. In this instance, information for at least one next-bestroute will be immediately available in the event of failure of thepreferred route. In an alternative embodiment, routing engine 305 maydetermine a next-best route only after the preferred route has failed.An advantage of the latter approach is that routing engine 305 may beable to better determine the next-best route with the benefit ofinformation concerning the most recent failure of the preferred route.

To facilitate alternative routing, and for other reasons, the routingengine 305 may maintain the state of each VoIP call in a call statelibrary 320. For example, routing engine 305 may store the state of acall as “set up,” “connected,” “disconnected,” or some other state.

Routing engine 305 may further format information about a VoIP call suchas the originator, recipient, date, time, duration, incoming trunkgroup, outgoing trunk group, call states, or other information, into aCall Detail Record (CDR). Including the incoming and outgoing trunkgroup information in a CDR may be advantageous for billing purposes overmerely including IP addresses, since IP addresses may change or behidden, making it difficult to identify owners of far-end networkresources. Routing engine 305 may store CDR's in a call state library320, and may send CDR's to the CDR engine 325 in real time, at thetermination of a call, or at other times.

The CDR engine 325 may store CDR's to a traffic database 330. Tofacilitate storage, the CDR engine 325 may format CDR's as flat files,although other formats may also be used. The CDR's stored in the trafficdatabase 330 may be used to generate bills for network services. The CDRengine 325 may also send CDR's to the traffic analysis engine 335.

Data necessary for the billing of network services may also be stored ina Remote Authentication Dial-In User Service (RADIUS) server 370. Infact, in some embodiments, the data stored in the RADIUS server may bethe primary source of billing information. The RADIUS server 370 mayalso directly communicate with a gateway 125 to receive and store datasuch as incoming trunk group, call duration, and IP addresses ofnear-end and far-end destinations. The CDR adapter 375 may read datafrom both the traffic database 330 and the RADIUS server 370 to create afinal CDR. The merged data supports customer billing, advantageouslyincluding information which may not be available from RADIUS server 370alone, or the traffic database 330 alone.

The traffic analysis engine 335 may collect CDR's, and may automaticallyperform traffic analysis in real time, near real time, or after apredetermined delay. In addition, traffic analysis engine 335 may beused to perform post-traffic analysis upon user inquiry. Automatic oruser-prompted analysis may be performed with reference to apredetermined time period, a specified outgoing trunk group, calls thatexceed a specified duration, or according to any other variable(s)included in the CDR's.

The provisioning engine 340 may perform tasks necessary to routeparticular calls over the Internet. For example, the provisioning engine340 may establish or modify client account information, authorize a longdistance call, verify credit, assign phone numbers where the destinationresides on a PSTIN network, identify available carrier trunk groups,generate routing tables, or perform other tasks. In one embodiment ofthe invention, provisioning may be performed automatically. In anotherembodiment, provisioning may be performed with user input. Hybridprovisioning, that is, a combination of automated and manualprovisioning, may also be performed. The provisioning engine 340 mayfurther cause provisioning data to be stored in a provisioning database345.

Client workstations 350 and 360 may be coupled to routing controller 200to provide a user interface. As depicted in FIG. 3, the client(s) 350may interface to the traffic analysis engine 335 to allow a user tomonitor network traffic. The client(s) 360 may interface to theprovisioning engine 340 to allow a user to view or edit provisioningparameters. In alternative embodiments, a client may be adapted tointerface to both the traffic analysis engine 335 and provisioningengine 340, or to interface with other features of routing controller200.

In a system embodying the invention, as shown in FIG. 2, the gateways125/126 would first receive a request to set up a telephone call fromthe PSTN, or from a Long Distance Provider 117, or from some othersource. The request for setting up the telephone call would typicallyinclude the destination telephone number. In order to determine whichdestination gateway should receive the packets, the gateway wouldconsult the gatekeeper 205.

The gatekeeper 205, in turn may consult the routing controller 200 todetermine the most appropriate destination gateway. In some situations,the gatekeeper may already have the relevant routing information. In anyevent, the gatekeeper would forward the routing information to theoriginating gateway 125/126, and the originating gateway would then sendthe appropriate packets to the appropriate destination gateway. Asmentioned previously, the routing information provided by the gatekeepermay include just a preferred destination gateway, or it may include boththe preferred destination gateway information, and information on one ormore next-best destination gateways. The routing information may alsoinclude a preferred route or path onto the Internet, and one or morenext-best route. The routing information may further include informationabout a preferred Internet Service Provider.

FIG. 4 is a flow chart illustrating a method embodying the invention forusing the routing controller 200. In step 400, the routing controller200 receives a routing request from either a gatekeeper, or a gateway.In step 405, a decision is made as to whether provisioning data isavailable to route the call. If the provisioning data is not available,the process advances to step 410 to provision the route, then to step415 for storing the provisioning data before returning to decision step405.

If, on the other hand, if it is determined in step 405 that provisioningdata is available, then the process continues to step 420 for generatinga route. In a preferred embodiment of the invention, step 420 may resultin the generation of information for both a preferred route, and one ormore alternative routes. The alternative routes may further be rankedfrom best to worst.

The routing information for a call could be simply informationidentifying the destination gateway to which a call should be routed. Inother instances, the routing information could include informationidentify the best Internet Service Provider to use to place the calltraffic onto the Internet. In addition, the routing controller may knowthat attempting to send data packets directly from the originatinggateway to the destination gateway is likely to result in a failed call,or poor call quality due to existing conditions on the Internet. Inthese instances, the routing information may include information thatallows the data packets to first be routed from the originating gatewayto one or more interim gateways, and then from the interim gateways tothe ultimate destination gateway. The interim gateways would simplyreceive the data packets and immediately forward the data packets on tothe ultimate destination gateway.

Step 420 may also include updating the call state library, for examplewith a call state of “set up” once the route has been generated. Next, aCDR may be generated in step 425. Once a CDR is available, the CDR maybe stored in step 430 and sent to the traffic analysis engine in step435. In one embodiment, steps 430 and 435 may be performed in parallel,as shown in FIG. 4. In alternative embodiments, steps 430 and 435 may beperformed sequentially. In yet other embodiments, only step 430 or only435 may be performed.

FIG. 5 is a flow diagram illustrating a method for maintaining a callstate, which may be performed by routing engine 305. After starting instep 500, the process may determine in step 505 whether a route requesthas been received from a gatekeeper or other source. If a routingrequest has not been received, the process may advance to a delay step510 before returning to decision step 505. If, however, it is determinedin step 505 that a route request has been received, then a call statemay be set to “set up” in step 515.

The process of FIG. 5 may then determine in step 520 whether a connectmessage has been received from a gatekeeper or other source. If aconnect message has not been received, the process may advance to delaystep 525 before returning to decision step 520. If, however, it isdetermined in step 520 that a connect message has been received, then acall state may be set to “connected” in step 530.

The process of FIG. 5 may then determine in step 535 whether adisconnect message has been received from a gate keeper or other source.If a disconnect message has not been received, the process may advanceto delay step 540 before returning to decision step 535. If, however, itis determined in step 535 that a disconnect message has been received,then a call state may be set to “disconnected” in step 545 before theprocess ends in step 550.

The process depicted in FIG. 5 will operate to keep the call state forall existing calls up to date to within predetermined delay limits. Inalternative embodiments of the invention, the call state monitoringprocess can monitor for other call states such as “hang-up,” “busy,” orother call states not indicated above. Moreover, monitoring for othercall states may be instead of, or in addition to, those discussed above.Further, in one embodiment, monitoring could be performed in parallel,instead of the serial method illustrated in FIG. 5.

FIG. 6 discloses a sequence of messages between an originating gateway,a routing engine, a call state library, and a destination gateway,according to a preferred embodiment of the invention. In operation ofthe network, the originating gateway may send a first request forrouting information, in the form of a first Admission Request (ARQ)message, to a routing engine within a routing controller. The requestwould probably be passed on through a gatekeeper logically positionedbetween the gateway and the routing engine in the routing controller.

Upon receipt of the routing request, the routing engine may store aset-up state in call state library. The routing engine may thendetermine a best route based upon one or more predetermined attributessuch as the selected carrier service provider, a desired Quality ofService (QoS), cost, or other factors. The routing engine may then sendinformation pertaining to the best route to the originating gateway,possibly via a gatekeeper, as a first ARQ response message. The gatewaywould then initiate a first call to a destination gateway using theinformation contained within the response message. As shown in FIG. 6,the destination gateway may return a decline message to the originatinggateway.

When the originating gateway receives a decline message, the gateway maysend a second request for routing information, in the form of a secondARQ message, to routing engine. Routing engine may recognize the call asbeing in a set up state, and may determine a next best route forcompletion of the call. Routing engine may then send a second ARQresponse message to the originating gateway. The originating gateway maythen send a second call message to the same or a newly selecteddestination gateway using the next best route. In response to the secondcall message, the destination gateway may return a connect message tothe originating gateway.

The routing engine may use a conference ID feature of the H.323protocol, which is unique to every call, in order to keep track ofsuccessive routing attempts. Thus, upon receiving a first ARQ for aparticular call, routing engine may respond with a best route; uponreceiving a second ARQ associated with the same call, routing engine mayrespond with the second best route. If the second call over the nextbest route does not result in a connection, the originating gateway maysend a third ARQ message to routing engine, and so on, until an ARQresponse message from routing engine enables a call to be establishedbetween the originating gateway and a destination gateway capable ofcompleting the call to the called party.

In alternative embodiments of the invention, the initial ARQ responsefrom the routing engine to the originating gateway may includeinformation about the best route, and one or more next-best routes. Inthis instance, when a call is declined by one terminating gateway, theoriginating gateway can simply attempt to route the call using thenext-best route without the need to send additional queries to therouting engine.

Once the originating gateway receives a connect message from adestination gateway, the originating gateway may send an InformationRequest Response (IRR) message to the routing engine to indicate theconnect. In response, the routing engine may store a connected statemessage to the call state library.

After a call is connected, a call may become disconnected. A disconnectmay occur because a party has hung up, because of a failure of a networkresource, or for other reasons. In this instance, destination gatewaymay send a disconnect message to the originating gateway. In response,originating gateway may send a Disengage Request (DRQ) message to therouting engine. The routing engine may then update the call state bystoring a disconnected state status in the call state library.

FIG. 7 is a flow diagram illustrating a method, according to a preferredembodiment of the invention, for generating routing information inresponse to a routing request. As shown in FIG. 7, when a routingcontroller (or a gatekeeper) receives a routing request from a gateway,the method first involves selecting a destination carrier that iscapable of completing the call to the destination telephone in step 702.In some instances, there may be only one destination carrier capable ofcompleting the call to the destination telephone. In other instances,multiple destination carriers may be capable of completing the call. Inthose instances where multiple carriers are capable of completing thecall, it is necessary to initially select one destination carrier. Ifthe call is completed on the first attempt, that carrier will be used.If the first attempt to complete the call fails, the same or a differentcarrier may ultimately be used to complete the call.

Where there are multiple destination carriers capable of completing thecall, the selection of a particular destination carrier may be based onone or more considerations including the cost of completing the callthrough the destination carriers, the quality of service offered by thedestination carriers, or other considerations. The destination carriermay be selected according to other business rules including, forexample, an agreed upon volume or percentage of traffic to be completedthrough a carrier in a geographic region. For instance, there may be anagreement between the system operator and the destination carrier thatcalls for the system operator to make minimum daily/monthly/yearlypayments to a destination carrier in exchange for the destinationcarrier providing a predetermined number of minutes of service. In thosecircumstances, the system operator would want to make sure that thedestination carrier is used to place calls for at least thepredetermined number of minutes each day/month/year before routing callsto other destination carriers to ensure that the system operator derivesthe maximum amount of service from the destination carrier in exchangefor the minimum guaranteed payment. Business rules taking onto accountthese and other similar types of considerations could then be used todetermine which destination carrier to use.

Once the destination carrier has been selected, the method would includeidentifying an IP address of a destination gateway connected to thedestination carrier and capable of passing the call on to thedestination carrier. The destination gateway could be operated by thesystem operator, or by the destination carrier, or by a third party.Typically, a table would be consulted to determine which destinationgateways correspond to which destination carriers and geographiclocations.

Often there may be multiple destination gateways capable of completing acall to a particular destination carrier. In this situation, the step ofdetermining the IP address could include determining multipledestination IP addresses, each of which correspond to destinationgateways capable of completing the call to the destination carrier.Also, the IP address information may be ranked in a particular order inrecognition that some destination gateways may offer more consistent orsuperior IP quality. Also, if two or more destination gateways capableof completing a call to a destination carrier are operated by differentparties, there may be cost considerations that are also used to rank theIP address information. Of course, combinations of these and otherconsiderations could also be used to select particular destinationgateways, and to thus determine the IP address(s) to which data packetsshould be sent.

In some embodiments of the invention, determining the IP address(s) ofthe terminating gateway(s) may be the end of the process. This wouldmean that the system operator does not care which Internet ServiceProvider (ISP) or which route is used to place data traffic onto theInternet. In other instances, the method would include an additionalstep, step 806, in which the route onto the Internet and/or the ISPwould then be selected. The selection of a particular ISP may be basedon a quality of service history, the cost of carrying the data, orvarious other considerations. The quality of service history may takeinto account packet loss, latency and other IP based considerations.Also, one ISP may be judged superior at certain times of the day/week,while another ISP may be better at other times. As will be described inmore detail below, the system has means for determining the quality ofservice that exists for various routes onto the Internet. Thisinformation would be consulted to determine which route/ISP should beused to place call data onto the Internet. Further, as mentioned above,in some instances, the routing information may specify that the calldata be sent from the originating gateway to an interim gateway, andthen from the interim gateway to the destination gateway. This couldoccur, for example, when the system knows that data packets placed ontothe Internet at the originating gateway and addressed directly to thedestination gateway are likely to experience unacceptable delays orpacket loss.

In some instances, the quality of service can be the overridingconsideration. In other instances, the cost may be the primaryconsideration. These factors could vary client to client, and call tocall for the same client.

For example, the system may be capable of differentiating betweencustomers requiring different call quality levels. Similarly, even forcalls from a single customer, the system may be capable ofdifferentiating between some calls that require high call quality, suchas facsimile transmissions, and other calls that do not require a highcall quality, such as normal voice communications. The needs and desiresof customers could be determined by noting where the call originates, orby other means. When the system determines that high call quality isrequired, the system may eliminate some destination carriers,destination gateways, and ISPs/routes from consideration because they donot provide a sufficiently high call quality. Thus, the system may makerouting decisions based on different minimum thresholds that reflectdifferent customer needs.

FIG. 8 shows a conceptual diagram of four gateways with access to theInternet. Gateway A can reach Gateways B and C via the Internet. GatewayC can reach Gateway D via the Internet, and Gateway B via an externalconnection. Due to Internet conditions, it will often be the case thatcertain Gateways, while having access to the Internet, cannot reliablysend data packets to other gateways connected to the Internet. Thus,FIG. 8 shows that Gateway C cannot reach Gateways B or A through theInternet This could be due to inordinately long delays in sending datapackets from Gateway C to Gateways A and B, or for other reasons.

The gateways illustrated in FIG. 8 could be gateways controlled by thesystem operator. Alternatively, some of the gateways could be maintainedby a destination carrier, or a third party. As a result, the gatewaysmay or may not be connected to a routing controller through agatekeeper, as illustrated in FIG. 2. In addition, some gateways mayonly be capable of receiving data traffic and passing it off to a localor national carrier, while other gateways will be capable of bothreceiving and originating traffic.

Some conclusions logically flow from the architecture illustrated inFIG. 8. For instance, Gateway B can send data traffic directly toGateway D through the Internet, or Gateway B could choose to send datato Gateway D by first sending the traffic to Gateway A, and then havingGateway A forward the traffic to Gateway D. In addition, Gateway B couldsend the traffic to Gateway C via some type of direct connection, andthen have Gateway C forward the data on to Gateway D via the Internet.

The decision about how to get data traffic from one gateway to anotherdepends, in part, on the quality of service that exists between thegateways. The methods embodying the invention that are described belowexplain how one can measure the quality of service between gateways, andthen how the quality measurements can be used to make routing decisions.

As is well known in the art, a first gateway can “ping” a secondgateway. A “ping” is a packet or stream of packets sent to a specifiedIP address in expectation of a reply. A ping is normally used to measurenetwork performance between the first gateway and the second gateway.For example, pinging may indicate reliability in terms of a number ofpackets which have been dropped, duplicated, or re-ordered in responseto a pinging sequence. In addition, a round trip time, average roundtrip time, or other round trip time statistics can provide a measure ofsystem latency.

In some embodiments of the invention, the quality of servicemeasurements may be based on an analysis of the round trip of a ping. Inother embodiments, a stream of data packets sent from a first gateway toa second gateway could simply be analyzed at the second gateway. Forinstance, numbered and time-stamped data packets could be sent to thesecond gateway, and the second gateway could determine system latencyand whether packets were dropped or reordered during transit. Thisinformation could then be forwarded to the routing controller so thatthe information about traffic conditions between the first and secondgateways is made available to the first gateway.

A system as illustrated in FIG. 8 can use the data collected throughpings to compare the quality and speed of a communication passingdirectly between a first gateway and a second gateway to the quality andspeed of communications that go between the first and second gatewaysvia a third or intermediate gateway. For instance, using the systemillustrated in FIG. 8 as an example, the routing controller could holdinformation about traffic conditions directly between Gateway B andGateway D, traffic conditions between Gateway B and Gateway A, andtraffic conditions between Gateway A and Gateway D. If Gateway B wantsto send data packets to Gateway D, the routing controller could comparethe latency of the route directly from Gateway B to Gateway D to thecombined latency of a route that includes communications from Gateway Bto Gateway A and from Gateway A to Gateway D. Due to local trafficconditions, the latency of the path that uses Gateway A as an interimGateway might still be less than the latency of the direct path fromGateway B to Gateway D, which would make this route superior.

In methods embodying the invention, each gateway capable of directlyaccessing another gateway via the Internet may periodically ping each ofthe other gateways. The information collected from the pings is thengathered and analyzed to determine one or more quality of serviceratings for the connection between each of the gateways. The quality ofservice ratings can then be organized into tables, and the tables can beused to predict whether a particular call path is likely to provide agiven minimum quality of service.

To reduce the amount of network traffic and the volume of testing, onlyone gateway within a group of co-located gateways may be designated as aproxy tester for all gateways within the co-located group. In addition,instead of pinging a far-end gateway, one might ping other Internetdevices that are physically close to the far-end gateway. These stepssave network bandwidth by reducing the required volume of testing. Also,the testing can be delegated to lower cost testing devices, rather thanexpensive gateways.

A quality of service measure would typically be calculated using the rawdata acquired through the pinging process. As is well known to those ofskill in the art, there are many different types of data that can bederived from the pinging itself, and there is an almost infinite varietyof ways to combine this data to calculate different quality of servicemeasures.

FIG. 9 is a diagram of a matrix of quality of service data thatindicates the quality of service measured between 10 different gateways,gateways A-J. This table is prepared by having each of the gateways pingeach of the other gateways. The data collected at a first gateway isthen collected and used to calculate a quality of rating between thefirst gateway and each of the other gateways. A similar process ofcollection and calculation occurs for each of the other gateways in thesystem. The calculated quality of service values are then inserted intothe matrix shown in FIG. 9. For instance, the quality measure value atthe intersection of row A and column D is 1.8. Thus, the value of 1.8represents the quality of service for communications between Gateways Aand D. When an X appears in the matrix, it means that no communicationsbetween the row and column gateways was possible the last time the pingswere collected.

Although only a single value is shown in the matrix illustrated in FIG.9, multiple quality of service values could be calculated forcommunications between the various gateways. In other words, multiplevalues might be stored at each intersection point in the matrix. Forinstance, pings could be used to calculate the packet loss (PL), latency(LA), and a quality of service value (Q) which is calculated from thecollected pinging data. In this instance, each intersection in thematrix would have an entry of “PL, LA, Q”. Other combinations of datacould also be used in a method and matrix embodying the invention.

The pinging, data collection and calculation of the values shown in thematrix could be done in many different ways. Two alternative methods areillustrated in FIGS. 10A and 10B.

In the method shown in FIG. 10A, pinging occurs in step 1001. Asdiscussed above, this means that each gateway pings the other gatewaysand the results are recorded. In step 1002, the data collected duringthe pinging step is analyzed and used to calculate various qualitymeasures. In step 1003, the quality metrics are stored into the matrix.The matrix can then be used, as discussed below, to make routingdecisions. In step 1004, the method waits for a predetermined delayperiod to elapse. After the delay period has elapsed, the method returnsto step 1001, and the process repeats.

It is necessary to insert a delay into the method to avoid excessivepinging from occurring. The traffic generated by the pinging processtakes up bandwidth that could otherwise be used to carry actual datatraffic. Thus, it is necessary to strike a balance between conductingthe pinging often enough to obtain accurate information and freeing upthe system for actual data traffic. In addition, the bandwidth used bytesting can also be managed by controlling the number of pings sent pertest. Thus, the consumption of bandwidth is also balanced against theability to measure packet loss.

The alternate method shown in FIG. 10B begins at step 1008 when thepinging process is conducted. Then, in step 1009, the system determineswhether it is time to recalculate all the quality of service metrics.This presupposes that the matrix will only be updated at specificintervals, rather than each time a pinging process is conducted. If itis not yet time to update the matrix, the method proceeds to step 1010,where a delay period is allowed to elapse. This delay is inserted forthe same reasons discussed above. Once the delay period has elapsed, themethod returns to step 1008 where the pinging process is repeated.

If the result of step 1009 indicates that it is time to recalculate thequality metrics, the method proceeds to step 1011, where thecalculations are performed. The calculated quality metrics are thenstored in the matrix in step 1013, and the method returns to step 1008.In this method, the matrix is not updated as frequently, and there isnot as high a demand for performing the calculations. This can conservevaluable computer resources. In addition, with a method as illustratedin FIG. 10B, there is data from multiple pings between each of thegateways for use in making the calculations, which can be desirabledepending on the calculations being performed. In some embodiments ofthe invention, once the Quality Metrics have been updated, the systemmay wait for a delay period to elapse before returning to step 1008 torestart the pinging process. Furthermore, the system may conduct acertain amount of pinging, then wait before calculating the metrics. Inother words, the pinging and calculating steps may be on completelydifferent schedules.

In either of the methods described above, the data used to calculate thequality metrics could include only the data recorded since the lastcalculations, or additional data recorded before the last set of qualitymetrics were calculated. For instance, pinging could occur every fiveminutes, and the quality metrics could be calculated every five minutes,but each set of calculations could use data recorded over the last hour.

FIG. 11 illustrates a met hod embodying t he invent ion for selectingand providing routing information to a gateway making a routing request.This method would typically be performed by the gatekeeper connected toa gateway, or by the routing controller.

In step 1102, a routing request would be received. In step 1104, thesystem would obtain a first potential route. This step could involve allof the considerations discussed above relating to the selection of adestination carrier and/or destination gateway and/or an ISP or routebetween the originating gateway and the destination gateway.

Once the first potential route is determined, in step 1106 the systemwould look up the quality metrics associated with communications betweenthe originating and destination gateways. This would involve consultingthe quality matrix discussed above. One or more quality values in thematrix relating to the first proposed route would be compared to athreshold value in step 1108. If the quality for the first routesatisfies the threshold, the method would proceed to step 1110, and theroute would be provided to the requesting gateway as a potential routefor completion of a call.

If the result of comparison step 1108 indicates that the quality ofservice metrics for the first route do not satisfy the threshold, thenin step 1112 the system would determine if this is the last availableroute for completing the call. If so, the method would proceed to step1114, where the best of the available routes would be determined bycomparing the quality metrics for each of the routes considered thusfar. Then the method would proceed to step 1110, where the bestavailable route would be provided to the requesting gateway.

If the result of step 1112 indicates that there are alternative routesavailable, the method would proceed to step 1116, where the qualitymetrics for the next available route would be compared to the thresholdvalue. The method would then proceed to step 1108 to determine if thethreshold is satisfied.

A method like the one illustrated in FIG. 11 could be used to identifymultiple potential routes for completing a call that all satisfy a basicthreshold level of service. The quality metrics associated with eachroute could then be used to rank the potential routes. Alternatively,the cost associated with each route could be used to rank all routessatisfying the minimum quality of service threshold. In still otheralternative embodiments, a combination of cost and quality could be usedto rank the potential routes. As explained above, the ranked list ofpotential routes could then be provided to the requesting gateway.

As also explained above, in providing a route to a gateway, the routingcontroller may specify either a direct route between the gateways, or aroute that uses an interim gateway to relay data packets between anoriginating and destination gateway. Thus, the step of identifying apotential route in step 1104 could include identifying both directroutes, and indirect routes that pass through one or more interimgateways. When interim gateways are used, the quality metrics for thepath between the originating gateway and the interim gateway and thepath between the interim gateway and the destination gateway would allhave to be considered and somehow combined in the comparison step.

In a system embodying the invention, as shown in FIG. 2, multipledifferent gateways are all routing calls using routing informationprovided by the routing controller 200. The routing information storedin the routing controller includes tables that are developed using themethods described above. The routing table indicates the best availableroutes between any two gateways that are connected to the system. Evenwhen there are multiple routing controllers that are a part of thesystem, all routing controllers normally have the same routing tableinformation. This means that each time a gateway asks for a route to adestination telephone number, the routing information returned to thegateway will be the same, regardless of which gateway made the routingrequest. As will be explained below, in prior art systems, the fact thatall gateways receive the same routing information can lead tounnecessary signaling and looping of call setup requests.

FIG. 12 shows the basic architecture of a system embodying theinvention. As shown therein, the PSTN 115 and/or a long distance carrier117 both deliver calls to a front end switch 450 of the system. Thecalls arrive at the front end switch 450 as a call set-up request tocomplete a call to the destination telephone 145. The front end switch450 or the Source Gateway 460 can then consult a route controller,wherein the route controller determines the most optimal route and agateway associated with the most optimal route, which can convert thecall into digital data packets and place the packets on to the Internetproperly addressed to the designation gateway 464. Additionally, adestination gateway may be chosen from a plurality of destinationgateways depending on such criteria as, but not limited to,compatibility, dependability, and efficiency. The route controller ranksthe routes from the most optimal to least optimal.

Once a route is identified, the call request would be formatted asdigital data packets that include header data with routing information.For example the header can include information such as the originatinggateway associated with the most optimal route, the destination gateway,and the destination telephone number. The Source Gateway 460 thenattempts to complete the call to the destination gateway.

Each of the individual gateways can place data traffic onto the Internetusing one or more routes or access points. In the system illustrated inFIG. 12, Source Gateway 460 can place traffic onto the Internet usingroute C or D. The First Transmitting Gateway 462 can place traffic onthe Internet using routes A and B. The Second Transmitting Gateway 463can place traffic onto the Internet using routes E and F. At any givenpoint in time, one or more of these routes can become inoperative orsimply degraded in performance to the point that making a voice callthrough the route results in poor call quality.

In prior art systems, when the front end switch 450 receives a callrequest for a call intended for the destination telephone 145 fromeither the PSTN 115 or the long distance carrier 117, the front endswitch would forward the call to one of the gateways so that the callsetup procedures could be carried out. For purposes of explanation,assume that the call request is forwarded to Source Gateway 460. Thegateway would then make a routing request to the routing controller forinformation about the address of the destination gateway, and the mostpreferable route to use to get the data onto the Internet. Again, forpurposes of explanation, assume that the routing controller respondswith the address of the destination gateway 464, and with theinformation that the best routes, in preferred order, are routes C, thenA, and then E.

With this information, Source Gateway 460 would first try to set thecall up to go to the destination gateway 464 via route C. Assume thatfor whatever reason, route C fails. Source Gateway would then consultthe routing information again and determine that the next best route isroute A. Thus, Source Gateway would forward the call on to the FirstTransmitting Gateway 462, which is capable of using route A.

When the First Transmitting Gateway 462 receives the call request, ittoo will consult the routing controller for routing information. Thesame information will be returned to the First Transmitting Gateway 462,indicating that the preferred routes are C, then A, then E. With thisinformation, the First Transmitting Gateway 462 believes that route C isthe best route, so the First Transmitting Gateway 462 would bounce thecall request back to Source Gateway 460, so that the call could be sentthrough route C. Source Gateway would receive back the same call requestit just forwarded on to the First Transmitting Gateway 462. Depending onthe intelligence of the Source Gateway, the Source Gateway mightimmediately send a message to the First Transmitting Gateway 462indicating that route C has already been attempted and that this routefailed. Alternatively, Source Gateway might again try to send the callvia route C. Again the route would fail. Either way, the call requestwould ultimately be bounced back to the First Transmitting Gateway 462with an indication that the call could not be sent through route C.

When the First Transmitting Gateway 462 gets the call request back fromthe Source Gateway, it would then consult its routing information anddetermine that the next route to try is route A. If route A is operable,the call could then be setup between the First Transmitting Gateway 462and the destination gateway 464 via route A. Although this processeventually results in a successful call setup, there is unnecessary callsignaling back and forth between the Source Gateway 460 and the FirstTransmitting Gateway 462.

Moreover, if the First Transmitting Gateway 462 is unable to set up thecall through route A, the First Transmitting Gateway 462 would againconsult the routing information it received earlier, and the FirstTransmitting Gateway 462 would send the call to the Second TransmittingGateway 463 so that the call can be placed onto the Internet using routeE. When the Second Transmitting Gateway 463 receives the call requestfrom the First Transmitting Gateway 462, it too would consult therouting controller and learn that the preferred routes are route C, thenroute A, then route E. With this information, the Second TransmittingGateway 463 would forward the call request back to the Source Gateway460 with instructions to place the call through route C, which wouldfail again. The Source Gateway 460 would then forward the call back tothe Second Transmitting Gateway 463. The Second Transmitting Gateway 463would then try to complete that call using the First TransmittingGateway 462 and route A. This too would fail. Finally, the SecondTransmitting Gateway 463 would send the call out using route E.

Because each of the gateways are using the same routing information,when one or more routes fail, there can be a large amount of unnecessarylooping and message traffic between the gateways as the a call requestis passed back and forth between the gateways until the call is finallyplaced through an operative route. In preferred embodiments of theinvention, special routing procedures are followed to reduce oreliminate unnecessary looping.

In preferred embodiments of the invention, if the call attempt fails,the call attempt returns to the Source Gateway 460. The Source Gateway460 can then query the route controller for a second most optimal route.If the second most optimal route is located through First TransmittingGateway 462, the route controller attaches a second set of headerinformation identifying the new route to the data packets that comprisethe call set up request. The new header information identifies the FirstTransmitting Gateway 462. The Source Gateway 460 then forwards thesecond call set-up request to the First Transmitting Gateway 462. TheFirst Transmitting Gateway 462 is configured to strip off the portion ofthe header data which identifies itself The First Transmitting Gateway462 then sends the call setup request on to the Destination Gateway 464.If the second call attempt fails, the data packets are returned to theSource Gateway 460 because the header data identifying the FirstTransmitting Gateway 462 has been removed. It should be noted that anygateway can be the Source Gateway 460 as long as it is associated withthe most optimal route. It should also be noted that any transmittinggateway may be configured to automatically strip off a portion of theheader that identifies itself.

To be more specific, if the route controller determined that route C isthe most optimal route, the translated header information inserted ontothe data packets containing the call setup request would include anidentification of the Source Gateway 460, because that is where theroute is located, plus the destination gateway 464, plus the destinationtelephone number. The Source Gateway 460 then attempts the call setup bysending the data packets to the Destination Gateway 464. If the callattempt is successful, the call connection is completed. However, if thecall attempt fails, for any reason, it is returned to the Source Gateway460.

The gatekeeper then queries the route controller for a second mostoptimal route. For example, in FIG. 12, the second most optimal routemay be route A, which is located through the First Transmitting Gateway462. The Source Gateway 460 would then insert new header information,consisting of the identification of the First Transmitting Gateway 462in front of the existing header information. The Source Gateway 460 thenforwards the call set-up request, with the new header information, tothe First Transmitting Gateway 462. The First Transmitting Gateway 462reads the header information and discovers that the first part of theheader information is its own address. The First Transmitting Gateway462 will then strip off its own identification portion of the header.The First Transmitting Gateway 462 then attempts a call setup to thedestination gateway 464. If the second call attempt fails, thedestination gateway 464 returns the call attempt to the Source Gateway460, because the remaining portion of the header only identifies theSource Gateway 460. Thus, rather than bouncing the call attempt back tothe First Transmitting Gateway 462, the failed call attempt would simplyreturn to the Source Gateway 460, which tracks route failure andremaining optimal route information. This method can eliminate or reduceunnecessary looping.

In a second embodiment, each of the gateways will know which routes areassociated with each gateway. Alternatively, this information may beprovided by the routing controller as needed. This means that the FirstTransmitting Gateway 462 would know that the Source Gateway 460 usesroutes C and D, and that the Second Transmitting Gateway 463 uses routesE and F. The gateways can then use this information to reduce oreliminate unnecessary looping.

For instance, using the same example as described above, when a callrequest comes in to place a call to destination telephone 145, theSource Gateway 460 would first try to send the call via route C. Whenthat route fails, the Source Gateway 460 would send the call request tothe First Transmitting Gateway 462 so that the First TransmittingGateway 462 could send the call via route A. In the prior art system,the First Transmitting Gateway 462 would have bounced the call requestback to the Source Gateway 460 because the First Transmitting Gateway462 would believe that route C is the best way to route that call. Butin a system embodying the invention, the First Transmitting Gateway 462would know that the Source Gateway 460 uses route C. With thisknowledge, and knowing that the call request came from the SourceGateway 460, the First Transmitting Gateway 462 would conclude that theSource Gateway 460 must have already tried to use route C, and thatroute C must have failed. Thus, rather than bouncing the call requestback to the Source Gateway 460, the First Transmitting Gateway 462 wouldsimply try the next best route, which would be route A. Similar logiccan be used at each of the other gateways to eliminate unnecessarylooping.

In another preferred embodiment, special addressing information can beincluded in the messages passing back and forth between the gateways.For instance, and again with reference to the same example describedabove, assume that the Source Gateway 460 first gets a call request tocomplete a call to destination telephone 145. The Source Gateway 460would try to send the call via route C, and route C would fail. At thispoint, the Source Gateway 460 would know that the next best route isroute A. In this embodiment, before sending the call request on to theFirst Transmitting Gateway 462, the Source Gateway 460 could encode aspecial addressing message into the call request. The special addressingmessage would inform the First Transmitting Gateway 462 that the callrequest should be sent via a specific route. In the example, the SourceGateway 460 would include addressing codes that indicate that the callrequest should be sent via route A, since that is the next best route.

When the First Transmitting Gateway 462 receives the call request, itwould read the special routing information and immediately know that thecall should be sent via route A. If route A is operable, the call willimmediately be sent out using route A. If route A is not available, theFirst Transmitting Gateway 462 would consult the routing controller anddetermine that the next route to try is route E. The First TransmittingGateway 462 would then send the call request on to the SecondTransmitting Gateway 463 with special addressing information that tellsthe Second Transmitting Gateway 463 to immediately try to place the callusing route E. In this manner, unnecessary looping can be eliminated.

The foregoing embodiments and advantages are merely exemplary and arenot to be construed as limiting the present invention. The presentteaching can be readily applied to other types of apparatuses. Thedescription of the present invention is intended to be illustrative, andnot to limit the scope of the claims. Many alternatives, modifications,and variations will be apparent to those skilled in the art. In theclaims, means-plus-function clauses are intended to cover the structuresdescribed herein as performing the recited function and not onlystructural equivalents but also equivalent structures.

1. A method for routing telephone calls over the Internet between anoriginating gateway and a destination gateway, comprising: identifyingat least one destination gateway that routes telephone calls to adestination telephone; selecting an optimal route from a plurality ofroutes, wherein each route includes an originating gateway that sendsdata packets to destination gateways, and wherein the originatinggateway on the optimal route comprises a source gateway; making a firstcall setup attempt by sending data packets containing a first call setuprequest from the source gateway to a destination gateway; receiving amessage from the destination gateway indicating that the first callsetup attempt has failed; inserting header data into digital datapackets containing a second call setup request; and making a second callsetup attempt by sending the digital data packets containing the secondcall setup request to a destination gateway from an alternateoriginating gateway other than the source gateway, wherein the headerdata inserted into the digital data packets containing the second callsetup request ensures that a message indicating that the second callsetup attempt has failed is sent from the destination gateway to thesource gateway, even though the digital data packets containing thesecond call setup request were sent to the destination gateway from analternate originating gateway other than the source gateway.
 2. Themethod of claim 1, wherein making a second call setup attempt furthercomprises: identifying an alternate route including the alternateoriginating gateway; inserting new header data into the data packetscontaining the second call setup request, wherein the new header dataidentifies the alternate originating gateway connected with thealternate route; and sending the data packets containing the second callsetup request to the alternate originating gateway connected with thealternate route.
 3. The method of claim 2, wherein making a second callsetup attempt further comprises: stripping off the header dataidentifying the alternate originating gateway connected with thealternate route from the data packets containing the second call setuprequest before sending the data packets containing the second call setuprequest from the alternate originating gateway.
 4. The method of claim3, wherein if the second call setup attempt fails, the method furthercomprises: identifying an additional alternate route; inserting newheader data into the data packets containing the call setup request,wherein the new header data identifies yet another different originatinggateway connected with the additional alternate route; sending the datapackets containing the call setup request to the originating gatewayconnected with the additional alternate route; stripping off the headerdata identifying the originating gateway connected with the additionalalternate route from the data packets containing the call setup request;and making a third call setup attempt by sending the data packetscontaining the call setup request from the originating gateway connectedwith the additional alternate route to the destination gateway, whereinif the third call setup attempt fails, data contained in the datapackets containing the third call setup request will ensure that amessage indicating that the third call setup attempt has failed will besent from the destination gateway to the source gateway, even thoughtthe third call setup request was sent from the originating gatewayconnected with the additional alternate route.
 5. The method of claim 1,wherein the inserting step comprises inserting header data thatidentifies an originating gateway, and a path onto the Internet.
 6. Themethod of claim 5, wherein the inserting step also comprises insertingheader data that identifies a destination gateway.
 7. The method ofclaim 1, wherein the inserting step comprises inserting header data thatidentifies a source gateway, an interim gateway and a destinationgateway.
 8. The method of claim 7, wherein the header data identifyingan interim gateway is stripped off the data packets containing the callsetup request by the interim gateway such that the informationidentifying the source gateway and the destination gateway is leftintact.
 9. The method of claim 1, wherein the step of selecting anoptimal route from a plurality of routes comprises selecting anoriginating gateway, and a path onto the Internet.
 10. The method ofclaim 9, wherein selecting a path onto the Internet comprises selectingan Internet Service Provider.
 11. The method of claim 1, wherein thestep of selecting a destination gateway comprises selecting an optimaldestination gateway and at least one additional destination gateway fromamong a plurality of candidate destination gateways.
 12. The method ofclaim 1, wherein the step of selecting a route comprises selecting anoptimal originating gateway an Internet Service Provider, and at leastone alternate originating gateway and Internet Service Provider.
 13. Asystem configured to route telephone calls over the Internet,comprising: a routing controller that generates routing information thatidentifies routes for communicating digital data packets bearingtelephone calls over the Internet; a source gateway configured toreceive the routing information and to insert header data into datapackets containing a call setup request, wherein the header data isconfigured to ensure that if a call setup attempt sent to a destinationgateway from an alternate originating gateway other than the sourcegateway fails, a message sent back from the destination gatewayindicating that the call setup attempt has failed will be sent to thesource gateway, even though the call setup request was sent to thedestination gateway from the alternate originating gateway.
 14. Thesystem of claim 13, wherein the routing controller generates routinginformation that includes an originating gateway and an Internet ServiceProvider.
 15. The system of claim 13, wherein the routing controllergenerates routing information that includes an optimal route, and atleast one additional route, and wherein the optimal route includes thesource gateway.
 16. The system of claim 13, wherein the system furthercomprises an interim gateway, and wherein the source gateway insertsheader data into the data packets containing the call setup request suchthat the header data identifies the source gateway, and the interimgateway, and wherein the source gateway forwards the data packets to theinterim gateway.
 17. The system of claim 16, wherein the interim gatewayreceives the data packets forwarded by the source gateway, removes theheader data identifying the interim gateway, and places the data packetsonto the Internet.